This invention is directed to numerically controlled machines and, more particularly, to machines directed to the contour and other forming of extruded and sheet metal parts.
Contour forming machines for forming contours in extruded and sheet metal structural elements or parts, such as body frames, stiffeners and stringers used in aircraft, for example, fall generally into two classes--stretch forming machines and roll forming machines.
Stretch forming machines cause the parts to yield under tension while being maintained in a plastic state. The parts are wrapped against a form block of the desired contour until the desired part contour is achieved. Because an individual form block is required for each part, stretch forming has the disadvantage of requiring considerable lead time for form block fabrication and testing. With most high-strength materials, springback factors must be experimentally developed and incorporated into the form block contour. In addition to the expense attendant to developing individual form blocks, and the considerable lead time involved, stretch forming has the further disadvantage of requiring the maintenance and storage of an expensive inventory of large, fairly complex tools. Moreover, stretch forming has the mechanical disadvantage that when a part is formed in tension it has a strong tendency to thin and neck, thus losing structural strength. In order to avoid this tendency, filler blocks and a variety of elongation control devices are frequently employed, all of which further increase the cost of contour forming using this process.
In roll forming machines a part is traversed through an arrangement of rolls that are progressively offset to impart increasing contour. The operator of the roll forming machine continues to increase the contour of the part by adjustment of the rolls until he determines, through frequent reference to a template or checking fixture, that the desired contour configuration has been achieved. Because only a small increment of the part is formed at a time, and because the geometric arrangement of the rolls provides a considerable leverage factor, roll forming facilities are smaller than comparable stretch forming facilities. Moreover, roll forming machines are considerably less expensive than corresponding stretch forming machines. However, classically, only uniplanar contours, as opposed to multiplanar contours, have been formed using roll facilities. One of the reasons only uniplanar contours, as opposed to multiplanar contours, have in the past been formed using roll forming facilities relates to the mechanism for controlling the position of the forming rolls. Generally this mechanism has only moved the forming roll along a single axis readily controlled by operator skill. Obviously, single axis control will, in general, prevent multiplanar contours from being formed using the forming mechanism of a roll forming machine. Another problem with roll forming machines utilized by the prior art relates to their inability to readily contour form parts with complex cross sections. Since many parts that must be contour formed have complex cross sections, this limitation, obviously, limits the usefulnes of such roll forming machines.
A further limitation of prior art roll forming machines in their inability to change part cross-sectional shape as a part is being contour formed. For example, they have not been used to vary the angularity of the leg of a T-shaped part as it is being contour formed.
Therefore, it is an object of this invention to provide a new and improved contour forming machine.
It is a further object of this invention to provide a contour roll forming machine wherein the forming rolls are position adjustable about more than one axis.
It is a still further object of this invention to provide a new and improved mechanism for positioning the forming rolls of a roll forming machine about a variety of axes.
It is a still further object of this invention to provide a roll forming machine including a mechanism that allows the roll forming machine to readily contour form parts with complex cross sections.
It is yet another object of this invention to provide a roll forming machine suitable for varying the cross-sectional configuration of a part as it is being contour formed.
It is still another object of this invention to provide a roll forming machine suitable for varying the thickness of selected region of a part as it is being contour formed.